Heat treating grid



July 17, 1962 L. C. BIXBY HEAT TREATING GRID Filed Sept. 6, 1960 IN V EN TOR.

United States Patent Ofilice I 3,044,755 Patented July 17, 1962 This invention relates to a heat treating grid and more particularly, to a light weight tray structure useful in supporting articles which are being heat treated, however, the invention is not necessarily so limited.

Structures used as supports or containers for objects being heat treated are known to have only a limited life. The chief factor limiting the life of these structures is the repeated heating and cooling which the structures experience. This heating and cooling causes the metal of the structure to expand and contract repeatedly and, whereever the structure is irregular in shape or has structural discontinuities, weakening and ultimate failure can be expected. The presence of welded joints in the structure can be a source of failure. Also, irregularly shaped parts which do not heat and cool uniformly are a likely source of failure.

An object of the present invention is to provide a heat treating grid or tray which is of weld-free construction such that failure due to the presence of welds in the structure is eliminated.

Another object of this invention is to provide a heat treating grid or tray which is constructed preponderantly of cylindrical rod and wire stock, such that the major part of the basket is constructed with components which will heat and cool uniformly thereby minimizing failure due to differential expansion and contraction of these components.

Still another object of this invention is to provide a heat treating grid or tray having substantially duplicate supporting surfaces such that the useful life of the tray is increased accordingly.

A further object of this invention is to provide a heat treating grid having a large supporting surface obtained with a minimum of material.

till a further object of this invention is to provide a heat treating grid having substantially duplicate supporting surfaces on the opposite faces thereof, the two surfaces cooperating to reduce the cross-sectional area of openings in the grid.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

In the drawings, FIGURE 1 is a perspective view illustrating the heat treating grid of this invention.

FIGURE 2 is a plan view of a sinuously shaped wire element employed in the heat treating grid.

FIGURE 3 is a fragmentary elevation view taken substantially in the direction of the arrows '3- 3 of FIGURE 2.

FIGURE 4 is a fragmentary perspective view illustrating a modification.

Referring to the drawing .in greater detail, the heat treating grid of FIGURE 1 includes a plurality of spaced supporting rods 19 arranged in substantially coplanar relation. Cooperating with the rods to form a generally rectangular lattice are a plurality of spaced parallel slats 12 extending transversely of the rods 19. In assembling the lattice, spaced apertures are located centrally in the broad sides of the slats 12 and the rods 16 are passed through these apertures. It will be noted that the rods it), which are of circular cross-section, have a diameter which is smaller than the width of the broad sides of the slats.

The extreme ends of the rods 1ft are upset or otherwise enlarged so that the adjacent slats 12 are trapped on the rods. A network comprising two sinuously formed wire elements 14 is located between each pair of adjacent slats 12, the network's serving to uniformly space the slats 12. One of the wire elements, designated 14a in FIGURE 1, is located primarily in a plane above that occupied by the support rods 10. The other Wire element, designated with the reference numeral 14b, is located primarily in a plane below that occupied by support rods 10. Referring to the wire 1 in, this wire, as it progresses between the adjacent tats 12 is looped downwardly about successive rods 10.

Similarly, the wire 14b as it progresses between'the slats 1.2 is looped upwardly about successive rods 10. In the assembled grid, the loops occur at the successive crests and valleys of the sinuously formed wires, the loops in the crests contacting one slat 12 and the loops in the valleys contacting the opposite slat 12.

In constructing the grid, each wire 14 is looped at equal intervals to form similar loops '16 therein. FIGURE 2 illustrates such a wire after it has been formed to a sinuous shape. There, it will be noted that the ascending segments 17a and the descending segments 1712, which connect the loops, are formed substantially straight. This is done to give the grid which is ultimately formed an increased resistance to lateral compressive forces. It will also be noted that the loop formation in the wires 14 is such that the ascending segments 17a have a shorter distance to travel than the descending segments 17b, even though these segments have substantially the same length. In view of this circumstance, the ends 19 of the segments 17a are turned horizontally such that these segments remain straight throughout most of their ascending course, notwithstanding their extra length.

With reference to FIGURE 1, it will be noted that the wires 14a are out of phase with the wires 14b. As a result, each ascending portion of one wire element crosses a descending portion of the other wire element. By virtue of this construction, the wire elements 14aand 14b cooperate to reduce the cross-sectional area of the openings in the grid structure.

The slats 12 also operate to reduce the size of the openings in the grid. Absent the slats 12, there would be relatively large rectangular openings located between each of the adjacent pairs of wires 14a and 14b. The slats 12 bisect these openings and thereby reduce their size. For some purposes, however, it may be desirable to eliminate the slats. The construction of this grid is such that the slats 12 may be eliminated without impairing the usefulness of the structure for applications involving light loads.

It can be observed in FIGURE 1 that the upper edges of the slats 12 are substantially coplanar with the upper planar surface defined by the wires 14a. Similarly, the the lower edges of the slats 12 are substantially coplanar with the lower planar surface defined by the Wires 14b.

With this construction, the slats and the wires cooperate to establish a substantially uniform supporting surface on each face of the grid. Since the surfaces at the op posite faces of the grid substantially duplicate one another, both surfaces have equal utility. This substantially doubles the useful life of the grid.

Frequently, grids of this type are employed in heat treating apparatus wherein the grids supporting articles to be treated are conveyed automatically through a furnace. Where conveyors are used, it is particularly important that the grids do not jam the operation of the conveyor. minimize jamming of the conveyor by providing rounded corners and smooth sides for the grid. Thus, each of the corners of the grid is protected with a rounded bumper 18 made of fiat bar stock. These bumpers are secured at one end by forming an inwardly directed flange 22 The present grid has been designed to spea /5e thereon having an aperture through which the endmost rod 19 passes. The opposite ends of the bumpers are turned inwardly to form rearwardly directed flanges 20 extending along the sides of the outermost slats 12. These flanges are provided with apertures through which the two endmost rods 10 pass, these rods being upset or otherwise enlarged externally of the flanges 29.

The sides of the grid are rendered substantially uniform by providing additional bumpers 24 thereon. Each of these bumpers is formed of flat bar stock and is provided with inwardly turned flanges 26 which parallel the outer sides of the outermost slats 12. As shown, each of the flanges 26 is provided with an aperture through which one of the rods 10 passes, the ends of these rods being upset externally of the flanges 26.

In constructing this grid, it is preferable that the slats 12, rods 10, wires 14 and bumpers 18 and 24 are all formed of the same material such that dif erential expansion and contraction of these components upon heating and cooling is minimized. As already known to those skilled in the art, the particular metal employed in the grid will depend upon the particular heat treating operation which is to be performed. Steel, tungsten, molybdenum and Inconel are examples of materials which may be employed satisfactorily in the present construction.

FIGURE 4 illustrates a modfication wherein a tubular stock has been substituted for the flat bar stock employed in the preferred embodiment. Thus, the slats 12 and the bumpers 18 and 24 of the preferred embodiment are replaced by tubular rods 30 and tubular bumpers 32 and 34 in the modification.

In constructing this grid, the tubular elements are provided with diametrically disposed apertures at appropriate intervals for receipt of the support rods 14) which pass therethrough. The diameter of the tubular elements is arranged such that the opposite sides of the grid are substantially planar as is the case with the preferred embodiment.

As appears in FIGURE 4, the bumper 32 has one end a 36 turned inwardly adjacent the end of one of the tubular elements 38. This reduces the space available to the associated Wire element 14a and the descending straight line segment of the 'wire element 14a must be shortened accordingly. This is accomplished by providing an elongated horizontal shoulder 36 adjacent the end of the associated wire element 14a, as shown. The construction of the two embodiments is otherwise substantially identical.

The use of tubular elements of the type employed in the modification results in a heat treating grid having still greater resistance to failure attributable to differential thermal expansion and contraction of the elements in the grid. In the preferred embodiment, the slats 12 and the bumpers, being of flat bar stock, tend to cool rapidly at the edges and slowly at the center of the stock. This differential cooling sets up stresses in the bar stock which may produce premature failure of the part.

One the other hand, the tubular elements of the modification tend to heat or cool uniformly from the outer surface to the inner surface thereof. As a result the opportunity for destructive stresses to develop in the tubular stock is materially reduced.

Although the preferred embodiment of this invention has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof, the method of manufacture and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, 1 claim:

1. A metallic heat treating grid comprising, in combination, a substantially rectangular, generally planar lat tice of parallel slats and transversely extending rods, the broad sides of said slats extending substantially normal to the plane of said lattice and said slats having spaced centrally located apertures in the broad sides thereof through which said rods pass, a pair of wire elements extending sinuously and out of phase with each other between each pair of slats and extending generally transverse to said rods, one of each pair of wire elements being disposed below the plane of said rods and being looped upwardly about successive rods, the other of each pair of wire elements being disposed above the plane of said rods and being looped downwardly about successive rods, said wire elements having crests contacting one slat at alternate rods in said lattice and valleys contacting an opposite slat at the intermediate rods in said lattice.

2. The grid according to claim 1 wherein said wire elements are formed with substantially straight segments interconnecting the crests and valleys thereof.

3. The grid according to claim 1 including bumper elements secured to the rods of said lattice, there being one bumper element curving around each corner of the lattice.

4. in metallic heat treating grid comprising, in combination, a substantially rectangular, generally planar, lattice of parallel tubular elements and transversely extending rods, the tubular elements having spaced pairs of diametrically disposed apertures therein through which said rods pass, a pair of wire elements extending sinuously and out of phase with each other between each pair of tubular elements and extending generally transverse to said rods, one of each pair of wire elements being disposed below the plane of said rods and being looped upwardly about successive rods, the other of each pair of wire elements being disposed above the plane of said rods and being looped downwardly about successive rods, said wire elements having crests contacting one tubular element at alternate rods in said lattice and valleys contacting an opposite tubular element at the intermediate rods in said lattice.

5. The grid according to claim 4 wherein said wire eletents are formed with substantially straight segments interconnecting the crests and valleys thereof.

6. The grid according to claim 4 including tubular bumper elements secured to the rods of said lattice, there being one bumper element curving around each corner of the lattice.

7. A metallic heat treating tray including a plurality of wire networks mounted on parallel, generally coplanar rods, each of said networks comprising a pair of wire elements extending sinuously and out of phase with each other in a direction generally transverse to said rods, one of said wire elements being disposed below the plane of said rods and being looped upwardly about successive rods, the other of said wire elements being disposed above the plane of said rods and being looped downwardly about successive rods, each of said wire elements having crests located at alternate rods and valleys located at the intermediate rods, said networks being disposed side by side along the length of rods.

8. The heat treating tray according to claim 7 wherein said wire elements are formed with substantially straight segments interconnecting the crests and valleys thereof.

9. The heat treating tray according to claim 7 wherein said networks are separated by slats extending transverse to said rods and occupying planes normal to said rods, said slats each having spaced centrally located apertures in the broad sides thereof through which the rods pass, the opposite edges of said slats cooperating with the wire elements disposed respectively above and below the plane of said rods to form substantially duplicate supporting surfaces above and below said rods.

10. The heat treating tray according to claim 7 wherein said networks are separated by elongate tubular elements extending transverse to said rods, said tubular elements each having spaced pairs of diametrically disposed apertures therein through which the rods pass, opposite sides of said tubular elements cooperating with the Wire elements disposed respectively above and below the plane of said rods to form substantially duplicate supporting surfaces above and below said rods.

References Cited in the file of this patent UNITED STATES PATENTS Harris Feb. 28, 1939 Garofolo Oct. 2, 1956 FOREIGN PATENTS Great Britain June 14, 1934 7 France Feb. 23, 1959 

